I'm currently looking at buying a '06 1500 QC 5.7 hemi and I have a few questions about how MDS works.

I know that MDS will drop down to 4 cyl. to conserve gas & to increase mpg, but if I buy this pickup, the first thing I would like to do to it is install aftermarket exhaust.

So my questions are:
How will MDS effect that nice loud rumble I want to achieve?
Do I have to turn off MDS when installing the new exhaust?
From what I found, the Diablo tuner can turn off MDS, but is this the only way or can a dealer turn it off?

Thanks in advance!

oh....and also, how will turning off MDS effect my gas mileage??

 

This has been beaten to death.....

MDS only kicks in at cruising speeds, something your exhaust won't make much noise at anyways. Besides that, the louder the exhaust, the worse the mds will sound. It will sound like a drowning helicopter. it effed up my ears constantly. i could not take it, not to mention the shifting of the OEM programming sucks donkey ballz. Get yourself a tuner to atleast alter the shift schedule as the shifts lag majorly and are very sluggish.<---This is something stock guys may disagree with and I myself didn't think a tuner could make THAT much of a difference, but it does.
disabling mds will obviously reduce gas consumption, but by a small margin, BUT a tuner will increase gas mileage. pros/cons.
You will not like a catback with mds. i can almost promise you that unless your catback is as quiet as stock.

 

I haven't seen MDS guys report what they get on the highway with MDS turned off. But I get better than 18 on the highway when not towing and I don't even have MDS as an option. And what does the EPA sticker on the hemi RAMS say now - something like 20 hwy, with MDS? Seems like a lot of aggravation for <2mpg. I guess if you drive a lot, it adds up. But I'm glad I don't have it. And if I did, I'd probably turn it off.

 

Like DirtyDog says you need to turn of the MDS when you add an exhaust. It sounds awful and it feels like you are shifting up and down all the time. I turned mine off a week after I installed my AT3030. That made a big difference in the way the truck drove. I have a super ships 3865 and I love the performance mode. I get anywhere from 13 to 15 mpg.

 

Yah after putting on my cat back approx a month after I bought the truck it sounded so ****ty that I drove around in tow mode just to disable the mds until I bought my superchips, the mds hasnt been back on the truck since then. I dont notice any worse MPG but Ive never actually sat down to calculate it. Last weekend I did 180kms (112miles) and that was from a full tank down to half a tank.. not many of those kms were on the highway, and approximately 50 of them were on the trails 4x4ing up hills and such so its not to accurate.. Like I always say, if you wand good MPG buy a honda civic, Im gettin sick of hearing all these people buying trucks cause they want to look cool and then bitch and moan when they are getting something like 10-15 mpg!!

 

thanks for all the info! and yeah i know that owning a 4x4 pickup isn't going to get the best gas mileage in the world but i'm ok with that.....basically, i was just curious how comparable the mileage was between a hemi with mds vs. one without.

 

If you only drive in the ideal MDS scenario, then you might see a noticeable difference? Maybe.... I installed an MDS light in my truck so I can tell when it's on (I don't have aftermarket exhaust), and I've tried adjusting my driving style to active the MDS whenever possible. My mileage appears to have gone up about 1 MPG. I don't really think it's worth it. However, my commute is all city.

joe

 

Well when i was running around with MDS on without a programmer i was only get 10 mpg. Now with it turned off im getting about 14 mpg. Also, I was running with just cats no muffler with MDS and it sounds fine. Just when its on running with 4 Cyl it sounds like a 4 cyl car

 

My MDS kicks in at any speed over 15mph.

 

Indeed, on the shop truck, MDS will kick in just cruising slowly thru town.... 25-30 mph.